US solar-powered plane begins historic cross-country flight

A solar-powered airplane that developers hope to eventually pilot around the world took off early on Friday from San Francisco Bay on the first leg of an attempt to fly across the US with no fuel but the sun's energy.

The plane, dubbed the Solar Impulse, departed shortly after 6 am local time from Moffett Field, a joint civil-military airport near the south end of San Francisco, heading first to Phoenix on a slow-speed flight expected to take 15 to 20 hours.

The spindly looking plane barely hummed as it took flight in the still northern California morning as the sun was just beginning to peek out over the Santa Cruz Mountains to the east.

After additional stops in Dallas, St Louis and Washington, DC, with pauses at each destination to wait for favorable weather, the flight team hopes to conclude the plane's cross-country voyage in about two months.

Swiss pilots and co-founders of the project, Bertrand Piccard and Andre Borschberg, will take turns flying the plane, built with a single-seat cockpit, with Piccard at the controls for the first flight to Arizona. He is tentatively scheduled to land in Phoenix at 1 am local time on Saturday. The project began in 2003 with a 10-year budget of $112 million and has involved engineers from Swiss escalator maker Schindler and research aid from Belgian chemicals group Solvay.